1. Field of The Invention
This invention relates generally to a gas delivery system for supplying a constituent in the vapor-phase, at low concentration in a carrier gas, such as for example arsine, hydrogen selenide, and/or hydrogen telluride, in a carrier gas such as helium, nitrogen, or argon, for manufacture of semiconductors wherein the vapor-phase constituent is employed as a dopant source material.
2. Description of the Related Art
In the manufacture of semiconducting materials and semiconductor devices, a variety of gaseous compounds such as arsine, hydrogen selenide, and hydrogen telluride are employed as dopant source materials. These gaseous compounds are hazardous in character, and as a result of toxicity and safety considerations, must be carefully handled in the semiconductor manufacturing facility.
In conventional practice, these gaseous compounds are supplied in the semiconductor manufacturing plant from high pressure gas cylinders. With such high pressure gas cylinders, there is the associated danger of cylinder rupture resulting in gross introduction of the hazardous gases into the ambient environment in the manufacturing facility. There is also the danger of leakage from such cylinders, due to defects in or damage to the cylinder heads, gas flow regulators, and associated flow circuitry.
As an example, in the manufacture of silicon-based semiconductor devices, arsine is employed as a dopant source material, for arsenic doping of epitaxial semiconductor films, at relatively low concentrations, on the order of from about 20 to about 100 ppm. Even though utilized in dilute gas mixtures for such application, the arsine is typically provided in pure bulk form in high pressure gas cylinders, which as indicated entails the risk of rupture of and/or leakage from the cylinders, with the attendant consequence of release of arsine into the surrounding environment in the manufacturing plant.
As an alternative to the conventional requirement of high pressure gas cylinders of arsine or other dopant source gases in the semiconductor manufacturing plant, it would be desirable to provide a liquid source compound for dopants such as arsenic, selenium, and tellurium, which would obviate such requirement. Unfortunately, however, no suitable liquid source compounds for these dopants have been produced which yield semiconductor materials with the desired superior electrical properties.
It would therefore be a significant advance in the art to provide a means and method for supplying gaseous hydridic compounds of arsenic, selenium, and tellurium, which obviate the requirement of high pressure gas cylinders as source apparatus for such gas compounds in semiconductor manufacturing operations.
It therefore is an object of the present invention to provide a gas delivery system for supplying a constituent in the vapor-phase, at low concentration in a carrier gas, which may be usefully employed to supply gaseous hydrides of arsenic, selenium, and tellurium, for use as dopant source materials in semiconductor manufacturing operations.
It is another object of the present invention to provide a system for supplying a gaseous component in dilute concentration in a carrier gas, which yields a highly precise concentration of such dilute component in the carrier gas mixture comprising same.
Other objects and advantages in the present invention will be more fully apparent from the ensuing disclosure and the appended claims.
Relative to the gas delivery system of the present invention, as described hereinafter, related art includes U.S. Pat. Nos. 4,723,967 and 4,738,693 of G. M. Tom, which disclose a vessel for semiconductor source reagent dispensing and/or purification in which liquid-filled permeation tubes may be provided, as described for example at column 10, lines 11-32 of U.S. Pat. No. 4,738,693. Other related art includes the following articles: R. N. Dietz and R. F. Wieser, "Sulfur Trioxide Permeation Tube for Calibration of Sulfuric Acid Measurement Methods," Anal. Chem. 51, 2388-23391 (1979); B. E. Saltzman, William R. Burg, and G. Ramaswamy, "Performance of Permeation Tubes and Standard Gas Sources," Environmental Science and Technology 5, 1121-1128 (1971); F. P. Scaringelli, A. E. O'Keeffe, E. Rosenberg, and J. P. Bell, "Preparation of Known Concentrations of Gases and Vapors with Permeation Devices Calibrated Gravimetrically," Anal. Chem. 42, 871-876 (1970); and A. Techentrup and D. Klockow, "Preparation of Refillable Permeation Tubes," Anal. Chem. 50, 1728 (1978).